Various methods are known in the art for optical 3D mapping, i.e., generating a 3D profile of the surface of an object by processing an optical image of the object. This sort of 3D profile is also referred to as a 3D map, depth map or depth image, and 3D mapping is also referred to as depth mapping.
PCT International Publication WO 2012/020380, whose disclosure is incorporated herein by reference, describes apparatus for mapping, which includes an illumination module. This module includes a radiation source, which is configured to emit a beam of radiation, and a scanner, which is configured to receive and scan the beam over a selected angular range. Illumination optics are configured to project the scanned beam so as to create a pattern of spots extending over a region of interest. An imaging module is configured to capture an image of the pattern that is projected onto an object in the region of interest. A processor is configured to process the image in order to construct a three-dimensional (3D) map of the object.
U.S. Patent Application Publication 2011/0279648, whose disclosure is incorporated herein by reference, describes a method for constructing a 3D representation of a subject, which comprises capturing, with a camera, a 2D image of the subject. The method further comprises scanning a modulated illumination beam over the subject to illuminate, one at a time, a plurality of target regions of the subject, and measuring a modulation aspect of light from the illumination beam reflected from each of the target regions. A moving-mirror beam scanner is used to scan the illumination beam, and a photodetector is used to measure the modulation aspect. The method further comprises computing a depth aspect based on the modulation aspect measured for each of the target regions, and associating the depth aspect with a corresponding pixel of the 2D image.
U.S. Pat. No. 8,018,579, whose disclosure is incorporated herein by reference, describes a three-dimensional imaging and display system in which user input is optically detected in an imaging volume by measuring the path length of an amplitude modulated scanning beam as a function of the phase shift thereof. Visual image user feedback concerning the detected user input is presented.
U.S. Pat. No. 7,952,781, whose disclosure is incorporated herein by reference, describes a method of scanning a light beam and a method of manufacturing a microelectromechanical system (MEMS), which can be incorporated in a scanning device.
U.S. Patent Application Publication 2013/0207970, whose disclosure is incorporated herein by reference, describes a scanning depth engine, which includes a transmitter, which emits a beam comprising pulses of light, and a scanner, which is configured to scan the beam, within a predefined scan range, over a scene. The scanner may comprise a micromirror produced using microelectromechanical system (MEMS) technology. A receiver receives the light reflected from the scene and generates an output indicative of the time of flight of the pulses to and from points in the scene. A processor is coupled to control the scanner and to process the output of the receiver so as to generate a 3D map of the scene.
Another time-of-flight scanner using MEMS technology is the Lamda scanner module produced by the Fraunhofer Institute for Photonic Microsystems IPMS (Dresden, Germany). The Lamda module is constructed based on a segmented MEMS scanner device consisting of identical scanning mirror elements. A single scanning mirror of the collimated transmit beam oscillates parallel to a segmented scanning mirror device of the receiver optics.